Our research is about the significance of polyunsaturated fatty acids (PUFAs) for human development. Specifically, we will assess the effect of docasohexanoic acid (DHA) supplementation during pregnancy on infant growth and development through a randomized controlled intervention trial in Cuernavaca, Mexico. This will be a collaborative effort among the Department of International Health, Rollins School of Public Health, Emory University, the Instituto Nacional de Salud Publica (INSP) and the Instituto Mexicano del Seguro Social (IMSS), Cuernavaca, Mexico. Pregnant women (n=994) attending the IMSS General Hospital I will be recruited at 20-24 wks gestation and assigned randomly to receive either DHA (200 mg) or a placebo daily until delivery. The main study endpoints include a) birth outcomes: birth size, gestational age, cord blood levels of DHA and neurodevelopment, b) maternal blood and breast milk DHA levels at 1 and 3 mo post-partum), c) postnatal growth and development during the first 18 mo of age and d) infant DHA status at 3, 12 and 18 mo. All data collection will be carried out at the study headquarters (IMSS) except for home environment that will be assessed during home visits at 6 and 12 mo. Physical growth (length, weight, and head circumference) and infant development (Brazelton & Fagan test, visual and auditory evoked potentials, and Bayley scales of infant development) will be measured at birth, 1, 3, 6, 9, 12 and 18 mo by trained nurses and psychologists, respectively. Data will also be obtained on socioeconomic status, obstetric history, maternal diet, anthropometry and intelligence, quality of home environment and infant feeding practices. Data analyses will include group comparisons (intent-to-treat) after ensuring effectiveness of randomization, and structural equation modeling to examine the various pathways by which DHA supplementation during pregnancy affects child growth and development. The findings of this project will contribute significantly to our understanding of the functional consequences of DHA supplementation during pregnancy.